The present invention relates to a method for controlling plasma density or its distribution over the target configuration of a magnetron source, a method for the production of coated workpieces, as well as magnetron sources.
Definition
By magnetron source is understood a sputter source, on which the discharge is operated with DC, AC or mixed AC and DC, or with pulsed DC, wherein AC is to be understood as extending up into the HF range. The source is conventionally operated under vacuum with a working gas, such as for example argon, at pressures of a few mbar up to 10−3 mbar. In known manner, reactive additional gases can be mixed in for reactive processes.
Over the sputter surface of the target configuration at a magnetron source, a tunnel-form magnetic field is generated, which, in a view onto the surface to be sputtered, the sputter surface, forms a closed loop. Viewed in the cross sectional direction of the target configuration, at least a portion of the magnetic field emerges from the sputter surface and enters back into it again in the form of a tunnel arch. The sputter surface, also referred to as the target surface, forms the one electrode, the cathode, of the plasma discharge gap, since positive ions must be accelerated onto the target surface for the sputtering process. This electrode can also be subdivided and its components can be individually electrically supplied.
Consequently, in the region of the loop of the tunnel-form magnetic field an electric field obtains, which is substantially at an angle with respect to the tunnel field. A tunnel-form electron trap results and a pronounced electron current, which substantially circulates in and along the loop of the tunnel-form magnetic field. In the region of said loop-form circulating magnetic field this electron current produces a pronounced increase of the plasma density compared to the plasma density further outside of said magnetic field loop.
Therewith along the circulating electron current, referred to in the technical field as “race track” a substantially increased sputter rate, results which leads to an increasingly more developed erosion trench in the sputter surface, i.e. at the base of the tunnel-form circulating magnetic field.
Apart from fundamentally the great advantages of magnetron sources, this increasingly developing erosion trench, has negative effects on                Coating homogeneity on the coated substrate,        Degree of utilization of the target material.        
In order to avoid at least partially these disadvantages, it is known to move, in particularly cyclically, entire or major portions of the magnetic field circulating tunnel-form in a loop with respect to the target configuration or its sputter surface. Thereby is obtained a temporal distribution of the “race track” electron current effect along the traversed sputter surface regions.
If it is taken into consideration that the looped magnetic field circulating in the form of a tunnel is conventionally realized by a configuration of strong permanent magnets beneath the target configuration, it is evident that, on the one hand, an existent permanent magnet configuration which, for shifting said magnetic field, is mechanically moved beneath the target configuration, can only be geometrically changed with relatively high expenditures, in order to realize different erosion profile distributions, and that in sputter operation a variation of this distribution or of the geometry of the permanent magnetic configuration is hardly possible.